The magnification scales on a Durst enlarger column

[Kirth Gersen]

I use a Durst Modular 70 Vario, and understand that the scales printed on the column are to tell me the magnification of the negatives I am working at dependent on lens size. My question is, what practical application of that knowledge is there? What is the purpose? There must be one, I just don't get it.

Pointers?

Thanks

Richard

 

[RalphLambrecht]

once the proper exposure is now for one magnification ,one for another can be simply calculated, eliminating the need for new test strips.

 

[Marco Gilardetti]

...but since calculations with minutes and seconds are often cumbersome and sometimes there's also an unpredictable input from reciprocity effect to be taken in account, you never trust the numbers on the column and you go for another test strip.

 

[MattKing]

...but since calculations with minutes and seconds are often cumbersome and sometimes there's also an unpredictable input from reciprocity effect to be taken in account, you never trust the numbers on the column and you go for another test strip.

Ah, but you use the calculations to determine the time range to use for your test strip, and can often use smaller increments.
If you do this frequently - make more than one print at different sizes from the same negative - you will find them useful.

 

[ic-racer]

Sometimes knowing your magnification values becomes a reality check. For example, comparing that 12X enlargement of a 35mm negative to the same-size 1.4X enlargement from an 8x10 negative.

 

[Kirth Gersen]

OK - I get it... sort of. It is currently not relevant for me as I am limiting myself to 10x8. But if I chose to blow up, say, to a larger print I would work out the new exposure values. Could someone offer a simple example?

 

[ic-racer]

The equation I use is:
new_time = old_time x (new_M +1)^2 / (old_M+1)^2
where M = new magnification (print/neg) and m = old
magnification (print/neg)

The exposure time factor would be:
Factor = (M + 1)^2 / (m + 1)^2

The equation has been verified with on-baseboard exposure meter testing.

 

[MattKing]

The equation I use is:
new_time = old_time x (new_M +1)^2 / (old_M+1)^2
where M = new magnification (print/neg) and m = old
magnification (print/neg)

The exposure time factor would be:
Factor = (M + 1)^2 / (m + 1)

The equation has been verified with on-baseboard exposure meter testing.

Shouldn't it be: Factor = (M + 1)^2 / (m + 1)^2

 

[ic-racer]

Shouldn't it be: Factor = (M + 1)^2 / (m + 1)^2

Nice pickup; cut and past error.

 

[Kirth Gersen]

Thanks both. Not exactly simple though .

 

[John51]

The magnification scales are there as a guide. Gives you an idea of where the head needs to be for x mag. Might as well have them as they were already printing the height scales which is the real value imo.

When you make a print, noting the height allows you to quickly replicate that % of magnification/crop should you decide to make an identical print later.

Useful for making contact prints as the head is positioned just high enough to cover 10x8. With an older round column enlarger, getting the same height every time is either 'near enough' or some form of measuring stick needs to be used.

 

[grahamp]

The scale also allows one to position the head roughly correct for any format for any image size. It saves some of the head position/focus, repeat dance.

How valuable it is depends on how one works - easy to ignore if you don't need it. In some ways it is better than the linear height on my Beseler 45.

 

[Sputnique]

I use a Durst Modular 70 Vario, and understand that the scales printed on the column are to tell me the magnification of the negatives I am working at dependent on lens size. My question is, what practical application of that knowledge is there? What is the purpose? There must be one, I just don't get it.

Pointers?

Thanks

Richard

Is the magnification number for the area or for the sides of the paper?

If I have a 4*5" (20 sq in) negative and the enlarger set to magnification 4, will it be 8*10 (80 sq in) inches on the paper or 16*20?

 

[ic-racer]

Imagine magnifying a segment of line.

A line is defined as a line of points that extends infinitely in two directions. It has one dimension, length.